Sergeant major

Images: 
P4162106a, 72ppi.jpg

I assume this is a blue-phase sergeant major.  But, look at the front dorsal-fin; it looks different than any I have seen on photos of sergeant majors.  It was feisty, and I assume it was protecting eggs.  I mention that in case its behavior and fin shape and placement are in any way related. 

Can you explain the unusual fin shape and placement? 

The photo was taken April 16, 2009 at Molasses Reef, Key Largo, 19 feet deep, visibility 25 feet, bottom temperature 76 degrees Fahrenheit. 

Thank You,

Marty

Sergeant major

This certainly appears to be a Sergeant major displaying breeding colors. The dorsal fin/dorsal area might likely be the result of an injury or a deformity.  -V Kells

Breeding colors

Thank you for your reply.  Are "breeding colors" just the blue phase, or is it something more?  And, are all the blue-phase sergeant majors male?

Thank You,

Marty

Hello. A phase typically

Hello. A phase typically refers to a color or pattern that is a result of sexual maturity or environment. Breeding colors/patterns occur during courtship, spawning and nesting. For example, many wrasses mature from the juvenile to initial to terminal phases. Another example: Coney have three phases related to the depth at which they live. The bicolored phase males adopt breeding patterns during courtship. 

Sergeant major males change to blue during courtship/spawning and nesting. The males build and defend nests. Once females are done depositing eggs, they leave the males to fan the eggs and ward off predetors.

Not to further confuse things, but many fishes also change colors from day to night, during feeding, resting, or when they are agitated. Hope this helps! - Vkells

Perfect answer

What a perfect answer.  Thank you.

Marty

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